Structure and oxygen storage capacity of Pd/Pr/CeO2-ZrO2 catalyst: effects of impregnated praseodymia

Praseodymium (Pr) was impregnated to CeO2-ZrO2 solid solution by an impregnation method. The as-obtained Pr modified CeO2-ZrO2 was impregnated with 1 wt.% Pd to prepare the catalysts. The structure and reducibility of the fresh and hydrothermally aged catalysts were characterized by X-ray diffraction (XRD), Raman, X-ray photoelectron spectroscopy (XPS), CO chemisorption and H2 temperature-programmed reduction (H2-TPR). The oxygen storage capacity (OSC) was evaluated with CO serving as probe gas. Effects of impregnated Pr on the structure and oxygen storage capacity of catalysts were investigated. The results showed that the aged Pr-impregnated samples had much higher OSC and better reducibility than the unmodified ones. The scheme of structural evolutions of the catalysts with and without Pr was also established. Partial of the impregnated Pr diffused into the bulk of CeO2-ZrO2 during ageing, which inhibited the sintering, and increased the amount of oxygen vacancies in CeO2-ZrO2 support. Furthermore, those impregnated Pr species which covered on the surface of the support obstructed the strong metal-support interaction between Pd and Ce so as to reduce the encapsulation of Pd as well as the back spill-over of the oxygen during the catalytic process.